- Synthesis and sensory characteristics of kokumi ?-[Glu]n-Phe in the presence of glutamine and phenylalanine: Glutaminase from bacillus amyloliquefaciens or aspergillus oryzae as the catalyst
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The transpeptidase activity of glutaminase from Bacillus amyloliquefaciens (GBA) and Aspergillus oryzae (GAO) to yield ?-[Glu]n-Phe peptides were verified for the first time. In the presence of Gln and Phe, ?-Glu-Phe and ?-Glu-?-Glu-Phe were synthesized by GAO, and ?-Glu-Phe, ?-Glu-?-Glu-Phe, ?-Glu-?-Glu-?-Glu-Phe, ?-Glu-?-Glu-?-Glu-?-Glu-Phe, and ?-Glu-?-Glu-?-Glu-?-Glu-?-Glu-Phe were synthesized by GBA. The Km values for the transpeptidation catalyzed by GBA and GAO were 47.88 and 153.92 mM (Phe as the acceptor), 84.89 and 236.47 mM (?-Glu-Phe as the acceptor), indicating that GBA had a greater affinity than GAO for Phe and ?-Glu-Phe in the transpeptidation reaction. The Km values for the transpeptidation catalyzed by GBA against acceptors, Phe and ?-[Glu](1≤na kokumi taste to commercial soy sauce and model chicken broth. The astringent threshold values (2.5-3.92 mM) were approximately 3-fold of the kokumi threshold concentrations (0.78-1.53 mM). ?-[Glu]n-Phe or the post-enzymatic reaction mixture enhanced the umami intensity of commercial soy sauce and model chicken broth.
- Yang, Juan,Sun-Waterhouse, Dongxiao,Cui, Chun,Dong, Keming,Wang, Wei
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- γ-Glutamyl-dipeptides: Easy tools to rapidly probe the stereoelectronic properties of the ionotropic glutamate receptor binding pocket
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γ-Glutamyl-dipeptides, built by condensing the distal carboxylate of L-Glu (or D-Glu) onto a series of differently functionalized amino acids, were prepared and used as tools for rapidly probing the stereo-electronic properties of iGluRs, searching for subtype-selective ligands.
- Tamborini, Lucia,Nicosia, Veronica,Conti, Paola,Dall'Oglio, Federica,De Micheli, Carlo,Nielsen, Birgitte,Jensen, Anders A.,Pickering, Darryl S.,Pinto, Andrea
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p. 8486 - 8492
(2016/11/28)
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- PH-Dependent hydrolase, glutaminase, transpeptidase and autotranspeptidase activities of Bacillus subtilis γ-glutamyltransferase
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γ-Glutamyltransferases (γ-GTs) are heterodimeric enzymes that catalyze the transfer of a γ-glutamyl group from a donor species to an acceptor molecule in a transpeptidation reaction through the formation of an intermediate γ-glutamyl enzyme. In our search for a γ-GT from a generally recognized as safe microorganism suitable for the production of γ-glutamyl derivatives with flavor-enhancing properties intended for human use, we cloned and overexpressed the γ-GT from Bacillus subtilis. In this study, we report the behavior of B. subtilis γ-GT in reactions involving glutamine as the donor compound and various acceptor amino acids. The common thread emerging from our results is a strong dependence of the hydrolase, transpeptidase and autotranspeptidase activities of B. subtilis γ-GT on pH, also in relation to the pKa of the acceptor amino acids. Glutamine, commonly referred to as a poor acceptor molecule, undergoes rapid autotranspeptidation at elevated pH, affording oligomeric species, in which up to four γ-glutamyl moieties are linked to a single glutamine. Moreover, we found that d-glutamine is also recognized both as a donor and as an acceptor substrate. Our results prove that the B. subtilis γ-GT-catalyzed transpeptidation reaction is feasible, and the observed activities of γ-GT from B. subtilis could be interpreted in relation to the known ability of the enzyme to process the polymeric material γ-polyglutamic acid.
- Morelli, Carlo F.,Calvio, Cinzia,Biagiotti, Marco,Speranza, Giovanna
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p. 232 - 245
(2014/01/23)
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